1. Field of the Invention
The present invention relates to a laser oscillator using a gas laser medium to be pumped by a light source, a heat source, an electric discharge or a chemical reaction for use in laser machining, medical treatment, illumination, communication, etc. and in particular to a laser oscillator having a function of reducing contamination of optical components in the oscillator by separating and collecting foreign matter in the gas laser medium.
2. Description of Related Art
FIG. 1 shows a general arrangement of a laser oscillator using a laser medium of fluid gas. In FIG. 1, excitation power sources 1 supply alternative current at a radio frequency band on electrodes of electric discharge tubes 2. The electric discharge tubes 2 are disposed between a rear mirror 3 and an output mirror 4 which are held by retainers (not shown). The electric discharge section 2 is incorporated into a circulating path including heat exchangers 5, 7 and a blower 6, through which gas laser medium 8 flows at high speed.
The excitation power source 1 is started to generate electric discharge in the electric discharge tubes 2 to pump the gas medium 8, to generate a laser beam. The gas medium 8 is heated to have a high temperature and cooled by the heat exchanger 5 before the blower 6 and flows into the blower 6 by suction. The blower 6 blows the gas medium 8 from an outlet thereof with pressure. The gas medium 8 is heated to raise its temperature by compression and is cooled again by a heat exchanger 7 provided downstream of the blower 6 to suppress rise of temperature of the gas medium 8. The gas medium 8 discharged from the blower 6 is supplied to the electric discharge section 2 through the heat exchanger 7.
In the above described laser oscillator, it is inevitable that particulate foreign matter such as dust is mixed into the gas medium 8 flowing in the circulating path because of various causes. For instance, in maintenance and production of dust by abrasion of parts in operations of the device and it is hardly possible to completely eliminate such causes. Once the particulate foreign matter is mixed into the gas medium 8, the particulate foreign matter circulates in the laser oscillator with the gas medium 8 without being eliminated, and is caught by the optical components such as the rear mirror 3 and the output mirror 4 to lower output of the laser oscillator and deteriorate the optical components.
Therefore, when the output of the laser power is lowered, it is necessary to clean the mirrors 3 and 4 by disassembling the laser oscillator which requires skill and considerable time to adjust the optical axis of the mirrors 3 and 4 which constitute the laser oscillator in reassembling the mirrors 3 and 4. In the case of a laser oscillator of high power, the mirrors 3 and 4 with the foreign matter caught may cause heat breakage by a local temperature rise when they are irradiated with the laser beam. It is necessary to change the mirrors with new ones, thereby increasing labor and the cost of maintenance.
An object of the present invention is to provide a laser oscillator having high reliability by reducing contamination of the optical components such as mirrors and requiring less maintenance of cleaning of the optical components.
A laser oscillator of the present invention has a circulating path for circulating gas laser medium subjected to laser pumping by a light source, a heat source, an electric discharge or a chemical reaction. The laser oscillator comprises a spiral flow section provided in the circulating path for producing a spiral flow of the gas laser medium to separate particulate foreign matter contained in the gas medium by centrifugal force generated in the spiral flow; and a dust collecting section arranged in the vicinity of the spiral flow section for collecting the separated particulate foreign matter by deposition.
The laser oscillator may further comprise an adjuster for adjusting pressure of the gas laser medium flowing in the circulating path in accordance with the diameter and/or mass of the particulate foreign matter to be separated and collected.
The spiral flow section may include a cylindrical body and an inner pipe arranged substantially coaxially with the cylindrical body to produce the spiral flow of the gas laser medium.
The inner pipe has an inlet opening to introduce the gas laser medium centrally in a cross-section perpendicular to an axis of the cylindrical body at an end portion of the spiral flow section.
The dust collecting section may be arranged below the spiral flow section, or laterally adjacent to the spiral flow section.
A slit may be formed between said spiral flow section and said dust collecting section to take the separated particulate foreign matter into the dust collecting section.
The slit may be formed at a peripheral position in the spiral flow section, and may be formed to extend substantially perpendicular to the spiral flow of the gas laser medium in the spiral flow section.
According to the present invention, particulate foreign matter contained in the gas laser medium is separated and collected by centrifugal force generated in the spiral flow of the gas laser medium, to prevent dispersion of the foreign matter in a laser resonator of the laser oscillator using the laser medium of fluid gas. Thereby, optical components are prevented from being contaminated by the particulate foreign matter in the gas laser medium, to elongate life of the optical components and prevent reduction of the laser output.